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Fan CFM Requirement Solver

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Input Parameters

Unit System

Room Dimensions

Volume: 8000 cu ft

Or Enter Volume Directly

Ventilation Requirements

Typical: Residential 4-8, Office 4-6, Kitchen 10-15

ASHRAE 62.1: Office 5 CFM, Retail 7.5 CFM

CFM Requirements

Required Fan Capacity

800
Design CFM CFM

Calculation Methods

ACH Method800 CFM
Occupancy Method150 CFM
Note: Using the higher of the two requirements

Calculation Breakdown

Room Volume8,000 cu ft
ACH Requirement6 ACH
Occupants10 people
Ventilation Rate15 CFM/person

Performance Metrics

CFM per sq ft0.80
Actual ACH6.0

Fan Selection Guide

Recommended Fan Size:880 CFM
(110% of calculated requirement for safety factor)
Fan Type Recommendations:
• Inline centrifugal fan recommended

CFM Requirements Analysis

Detailed Fan Analysis & Selection

Ventilation Analysis

ACH Dominance:ACH Controls
Ventilation Efficiency:84%
Air Density:0.075 lb/ft³
Mass Flow:60.0 lb/min

Fan Selection Criteria

Static Pressure:0.25-0.5 in WG
Motor HP (est):0.05 HP
Noise Level:Medium
Control Type:Variable

Energy Analysis

Annual Runtime:8760 hrs
Energy Cost/yr:$39
CO₂ Impact:280 lbs/yr
• Consider VFD for energy savings

Fan Sizing Options

Fan SizeCFMMotor HPAnnual CostRecommendation
100%8000.05$39Minimum
110%8800.06$43Recommended
125%1,0000.06$49Oversized

Fan CFM Calculation Steps

1

Determine Room Volume

Formula:
V=L×W×HV = L \times W \times H
Calculation:
V=8000 (given)V = 8000 \text{ (given)}
Result:
8000 cu ft8000 \text{ cu ft}
2

Calculate CFM based on Air Changes per Hour

Formula:
QACH=V×ACH60Q_{ACH} = \frac{V \times ACH}{60}
Calculation:
QACH=8000×660Q_{ACH} = \frac{8000 \times 6}{60}
Result:
800 CFM800 \text{ CFM}
3

Calculate CFM based on Occupancy

Formula:
Qocc=Npeople×VrateQ_{occ} = N_{people} \times V_{rate}
Calculation:
Qocc=10×15Q_{occ} = 10 \times 15
Result:
150 CFM150 \text{ CFM}
4

Determine Design CFM (higher of ACH or occupancy requirement)

Formula:
Qdesign=max⁡(QACH,Qocc)Q_{design} = \max(Q_{ACH}, Q_{occ})
Calculation:
Qdesign=max⁡(800,150)Q_{design} = \max(800, 150)
Result:
800 CFM800 \text{ CFM}
5

Calculate CFM per Square Foot

Formula:
QA=QdesignAfloor\frac{Q}{A} = \frac{Q_{design}}{A_{floor}}
Calculation:
QA=8001000\frac{Q}{A} = \frac{800}{1000}
Result:
0.80 CFM/ft²0.80 \text{ CFM/ft²}